Look on the inside of the radiator shroud for a small control unit with two rigid vacuum lines running to it ( think one is purple and one is white) with rubber elbows on the ends and an electrical connector. Slide it out and take a look at the elbows for dry rot and remove the connector and clean the contacts. Mine kept setting this code until I shot in some contact cleaner after which the light just went off on its own. Make sure your gas cap is tight and that the rubber seal isn't falling apart. Hope this helps

bruce